Fix video mirroring issue

[freddyaboulton]

Description

Fixes #1804

There are two problems that I found:

1. When source="upload", the front-end was flipping videos since mirror_webcam is always set to True in the config. Regardless of whether the source is a webcam. This is the problem causing Video mirroring #1804.
2. When the source is webcam and the format is specified (not None), the video was not flipped in the backend. There isn't an issue about this filed I think.

Issue 1 Test code

import gradio as gr

def video_test(video):
    return video

inputs_video_p5 = gr.Video(format="mp4", source="upload", label="原始视频")  # webcam
outputs_webcam_p5 = gr.Video(format='mp4', label="检测视频")

gyd = gr.Interface(
    fn=video_test,
    inputs=[inputs_video_p5],
    outputs=[outputs_webcam_p5],
)
gyd.launch(
    inbrowser=True,
)

Issue 2 Test Code

import gradio as gr

def video_test(video):
    return video

inputs_video_p5 = gr.Video(format="mp4", source="webcam", label="原始视频")  # webcam
outputs_webcam_p5 = gr.Video(format='mp4', label="检测视频")

gyd = gr.Interface(
    fn=video_test,
    inputs=[inputs_video_p5],
    outputs=[outputs_webcam_p5],
)
gyd.launch(
    inbrowser=True,
)

Checklist:

• I have performed a self-review of my own code
• I have added a short summary of my change to the CHANGELOG.md
• My code follows the style guidelines of this project
• I have commented my code in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

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[github-actions]

All the demos for this PR have been deployed at https://huggingface.co/spaces/gradio-pr-deploys/pr-2475-all-demos

[freddyaboulton]

Consolidating the two FFmpeg calls into one.

[pngwn]

Code looks good but I could never reproduce this, so will leave for someone else to test. It works fine for me, but it always did.

[abidlabs]

Nit:

Suggested change

	flip = self.source == "webcam" and self.mirror_webcam is True
	flip = self.source == "webcam" and self.mirror_webcam

[abidlabs]

Would this work?

Suggested change

	f"{file_name.name.replace(file_name.suffix, '')}{flip_suffix}{format}"
	f"{file_name.stem}{flip_suffix}{format}"

[freddyaboulton]

Yes!

[abidlabs]

Looks awesome @freddyaboulton!

[freddyaboulton]

Thanks for the review all!